This invention relates to pulverisers of the kind comprising a barrel having an open top for infeed of material to be pulverised and a bottom outlet for departure of pulverised material, an upright rotor rotatable within the barrel, and a plurality of hammers mounted on the rotor.
Within known pulverisers of this kind in which the wall of the barrel is relatively free of obstruction, the pulverising action is unsatisfactory for non-frangible, particularly light, tough materials, such as plastics and paper, since they remain practically intact after the pulverising process.
Such pulverisers also suffer from the disability effectively to deal with feed materials containing rags, cords and such like which tend merely to wind about the rotor and frequently cause jamming. Moreover, in use, the "granularity", that is to say, the size of the particulate material produced by such pulverisers, steadily increases as a result of the increase in spacing between the hammer tips and the barrel, due to hammer wear.
Pulverisers are known in which stationary baffles, striker plates or striker bars are fixed to the wall of the barrel. In such cases, the stationary striker bars are in the nature of cantilevers which, in use, are constantly subjected to shock or impact loading, and, as with any cantilever, the maximum bending moment occurs at the point of support. It follows that the cantilever supports have to be robust to withstand the loadings in question. This requires the barrel to be of massive construction and consequently such pulverisers generally have a very much higher weight to power ratio than pulverisers which do not have stationary blades. The total weight of such pulverisers, due largely to the massive barrel construction, has proved to be a serious disability for many applications. For example, as a result it has been very difficult, if not impossible, to mount such pulverisers on a vehicle such as a garbage collection vehicle, notwithstanding the fact that it is known to be desirable for material such as garbage to be pulverised before being compacted in the vehicles holding receptacle in order to increase the total quantity of material that the vehicle may accept.
A further disadvantage of known pulverisers of the type under discussion springs from the fact that the optimum spacing of the rotatable hammers from the barrel wall or from stationary strikers fixed to the barrel wall, varies according to the feed material. Thus, for optimum efficiency in pulverising aluminium cans, it is desirable that the clearance space between rotatable hammers and the barrel wall or stationary strikers is less than if garbage or glass are to be pulverised, while for optimum efficiency in pulverising steel cans the clearance is intermediate between the optimum for aluminium and the optimum for glass. Known pulverisers of this type are therefore generally inefficient for handling a wide range of different infeed material types.